The invention relates to a method for the automatic control of the setting of spinning rolls in relation to a cylindrical, tubular workpiece in an opposed roll spinning lathe with four pairs of rolls. More specifically, the invention relates to a method in which each of the four pairs of rolls consists of one inner roll each and one outer roll, of which is arranged on a holder on a carrier so as to be radially adjustable in relation to the workpiece and so that the pairs of rolls are arranged at an equal circumferential spacing about the workpiece with the roll pair acting as the first rolling stage placed diametrically opposite the second roll pair operating as the second rolling stage, and with the roll pair operating as the third rolling stage offset by 90.degree. in relation to the first roll pair and diametrically opposite the roll pair operating as the fourth rolling stage so that during the spinning rolling process the pairs of rolls and the workpiece perform a translatory and a rotary motion. Furthermore the radial forces acting on the rolls are continuously measured.
The invention takes as its starting point an opposed roll spinning lathe in accordance with the German pre-examination specification 3,545,506, and its equivalent U.S. Pat. No. 4,766,752 which operates with four pairs of rolls consisting respectively of an inner roll and an outer roll each of which is arranged radially adjustably in relation to the work on a holder secured to a carrier. The four pairs of rolls are evenly arranged about the circumference of the work and the roll pair forming the first rolling stage is diametrically opposite the second roll pair stage while the third roll pair stage is spaced by 90.degree. from the first and second roll pairs with the fourth roll pair diametrically opposite it. In this design of spinning and rolling lathe both the work drive and also the guides and feed drives of the inner and outer spinning roll carriers are arranged on the same side of the lathe and accommodated spatially on the foundation. The inner and outer spinning roll carriers are not connected with each other at the top end so that a substantial length of the tubular workpiece is free during spinning and is able to "grow" out of the spinning lathe in an upward direction. This type of spinning lathe is used for the spinning of tubes with a substantial diameter and length, the diameter of a tube to be produced being for instance of the order of three meters. In the case of such cold working to produce such tubes, extremely high rolling forces are required at the spinning rolls, for instance of the order of 300 to 2000 kN. It generally proves to be extremely difficult to apply such forces by means of cantilever roll carriers. Errors in computing and setting the working parameters of unforeseen events may quickly lead to severe damage to the spinning lathe.